Last Updated: February 25, 2016
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2.095K
· aleclanter

JavaScript parseInt and default radix

I learned the hard way that JavaScript's parseInt(string) method assumes any value with a leading '0' is in base8. To complicate matters, there is a bug in the way Chrome's JavaScript engine deals with base 8 numbers. I had the following two use cases:

var month1 = parseInt("04");
var month2 = parseInt("08");

month1 was coming back as expected, (int)4, but month2 was coming back as 0. Changing to an explicit radix of 10 fixes the issue:

var month2 = parseInt("08",10);

So, watch out for leading zeros mucking with your string-to-int conversions. And someone should let the Chrome JS engine's devs know that '08' is not 0 in base 8, it should be NaN. ;)